terrain and structures such as signs, roadways, trees, and buildings,...http://www.google.ca/patents/US6066439?utm_source=gb-gplus-sharePatent US6066439 - Instrument for photoerasable markingAdvanced Patent SearchPublication numberUS6066439 APublication typeGrantApplication numberUS 09/204,774Publication date23 May 2000Filing date3 Dec 1998Priority date5 Aug 1993Fee statusLapsedAlso published asUS